casting question

First of all I been casting wheel weight bullets for many years and never had this issue.Lately to streach my wheel weight supply, I tried to mix wheel weights 50/50 with range lead.My melt produced a sludge like heavy lead like substance that doesn't mix with the lead.A guess would be about 20% of the melt was this substance.Sturing didn't help,the sludge just floated back to the top of the melt.When I smelted,fluxed and poured the raw lead into the Lyman ingot mold for later use I never noticed this sludge.The mixing was in the production pot not the ingots.Any ideas? thanks hdbiker

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35 Whelen

May 25, 2013, 11:03 AM

What temp are you casting at? Sounds like you may have gotten some zinc in the mix. I smelt at around 650 - 700° and if there is any zinc or other foreign matter it floats to the top where it can be removed. Bottom line, zinc melts at around 785°, so smelt at temps well below this. I bought a temp probe for my digital voltmeter and use it to monitor alloy temp when smelting.
I can't imagine any range scrap that would cause sludge like you described.
35W

Don McDowell

May 25, 2013, 11:22 AM

Wondering if some of your range lead had moly lube on it? Sometimes lube from recycled bullets can make a mess out of a pot full of melt. Was the range lead raw or had it been melted into ingots already?
Zinc usually floats to the top and is a grey powdered looking stuff, and that could be what you have, skim it off and keep stirring to get it out of the melt.

243winxb

May 25, 2013, 11:23 AM

I would run my Lee 10 lb pot at maximum heat . Flux, skip off stuff on top & cast at high temperature till i get frosted bullets. If you cant get fill out of the bullet, they(castboolits) say saw dust will remove zinc?? If that fails, alloy is scrap.

zxcvbob

May 25, 2013, 11:39 AM

I'm processing a bunch of range lead now, in small batches on a hotplate. If I stir it and it's not quite hot enough (in technical terms, below the liquidus point) it is grainy and lumpy and tries to separate, and it sticks to the dross. Two problems: the temperature is too low, and the indoor range lead that I'm using has a lot of fine lead particles (almost dust) that is oxidized.

I add a handful of sawdust and let that char (it also insulates the top) and then stir it in, and use a ladle to pour the lead thru the ash and smoldering sawdust. This reduces the oxides back to lead and tin metal, and removes some of the copper, iron, calcium, etc. impurities. I sometimes add a little piece of candle wax and ignite it when I do this. The lead gets nice and fluid so I can pour my ingots.

1. Increase temp a bit, as the others have said, and flux well from the start.

2. Zinc increases the surface tension of the alloy, a little. This can make it look like the mold is filled when it really isn't. Wherever you stop pouring, the alloy can cling over the sprue hole, looking like it's overflowing, but there's still air underneath. So make sure you keep filling until the lead actually starts to overflow.

3. Be especially careful that your mold is closed all the way before each pour. (Before you close the sprue plate, look to see that the bullet nose-line is completely closed.) Zinc contamination makes little bits of alloy prone to sticking to the insides of the mold halves and mold alignment pins. If you don't stay on top of this, you will have a bunch of oversize bullets that are not quite finned, thus difficult to sort out.

4. Cuz of the higher temps, you will need to flux more often. Also, avoid dropping the sprues back in as you go. This mixes the zinc crud on the top back into the alloy.

Innovative

May 26, 2013, 05:13 PM

hdbiker .......

Lead is one of the heaviest elements, and anything that is not compatible with lead will float on top of it. You should flux your molten lead often. I flux with Borax, and I've found that it will mix anything that is compatible with lead into a good alloy for casting bullets.

That should separate incompatible metals, and anything that floats should be skimmed off and discarded.

It's best to melt your lead supply into ingots all at once. This produces the most uniform bullet weight.

Invaluable resource and so much info I could not begin to even repeat accurately.

I recall one member stating something to the effect of oxidized lead not mixing in properly, he thought it was zinc, skimmed it off, took it to the scrap yard and had it analyzed and came back as lead. He went home fluxed 2-3 times and smashed the oatmeal lumpy looking lead against the side of the pot and it mixed right in.

I live in Washington state so there are a lot of people up here (me included) who crab and shrimp. I'm going to start using my skimmed off crub to make crab/shrimp pot weights.

rcmodel

May 28, 2013, 04:19 PM

Crystalline sludge on top is most often unmelted Antimony from the wheel weights.

Up the pot temp and flux & stir some more.

rc

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